The overall goal of the project is to improve resolution achievable with large aperture phased linear arrays used in clinical ultrasound. In particular means will be developed which will eliminate beamforming errors caused by variations of sound velocity in the organs being imaged or by phase errors in the system hardware itself. It is believed that the current generation of clinical instruments fails to achieve its potential resolution due to these sound speed variations. More specifically feasibility of adaptive beamforming techniques to correct for the resulting phase errors will be evaluated. Algorithms derived from adaptive optics and others will be modified for use in medical ultrasound. Application of a successful algorithm in commercial instruments during Phase II of the project should establish a new performance level for image quality. Further, with use of these algorithms, tissue beds currently inaccessible to ultrasound may become new areas for ultrasonic diagnoses. An example of this is the brain where the extreme sound velocity in the skull reduces the potential for successful beam formation. As a consequence it is clear that potential for commercial success of such instruments is real and significant.